This invention relates to a thermal management system for an aircraft fuel system, and more particularly, the invention relates to a spool valve for the thermal management system that regulates the flow of fuel to the oil coolers and fuel tank for maintaining a desired temperature of fuel within the system.
The fuel systems of gas turbine engines typically include a return to tank function in which fuel is recirculated back to the main fuel tank using it as a heat sink to dissipate excess heat within the fuel system. Maintaining the fuel within the aircraft fuel system within a particular temperature range is necessary for desired operation of the components and overall aircraft engine and fuel system integrity. Fuel tank materials are sensitive to excessively hot fuel. Accordingly, the return to tank function must be capable of being shut completely off with no leakage. The slightest amount of leakage to the fuel tank could be detrimental. The prior art has utilized a separate, stand-alone shutoff valve to shut the flow of fuel off during the return to tank function. It is a relatively simple task to ensure that no fuel flows to the tank with a standalone valve. Numerous other valves within the fuel system are used to regulate the flow and pressure of the fuel to various components.
There is an effort to simplify aircraft systems, like many other systems in industry, to reduce components and cost. Therefore, it is desirable to simplify the aircraft fuel system and reduce the number of valves and components if at all possible. However, the need for providing a shutoff valve to the fuel tank that ensures that no leakage will occur is difficult to integrate with other valves. To this end, what is needed is an integrated shutoff valve providing a simplified thermal management system for an aircraft fuel system.
The present invention provides a thermal management system for an aircraft fuel system including a plurality of fuel pressure sources. A spool valve is fluidly connected to the pressure sources and is movable between a plurality of positions in response to the pressure sources. An oil cooler is fluidly connected to the spool valve with fuel flowing through the spool valve to the oil cooler in response to the spool valve being in one of the positions. The fuel tank is fluidly connected to the spool valve with fuel flowing to the spool valve to the fuel tank in response to the spool valve being in another of the positions. The spool valve moves to a closed fuel tank output position response to the pressure sources. The spool valve includes a housing having a bore with the plurality of pressure inputs and oil cooler and fuel tank outputs fluidly connected to the bore. A spool is disposed within the bore and is movable axially relative thereto between oil cooler, open fuel tank and the closed fuel tank outward positions. A valve assembly including a piston and target piston is disposed within the bore and is movable axially relative thereto. The valve assembly coacts with the spool to provide the closed fuel tank output position. A seal is arranged between the spool and the valve assembly sealing the spool and the valve assembly in the closed fuel tank output position to ensure that no fuel is permitted to leak back to the fuel tank.
Accordingly, the above invention provides a simplified aircraft fuel system with an integrated fuel tank shutoff valve.